1. Field of the Invention
The invention concerns a method of operating an internal combustion engine coupled to a generator in the event of a grid fault of a power supply grid connected to the generator, in particular in the event of a dynamic grid voltage drop, wherein the internal combustion engine includes a turbocharger having a compressor in an air feed duct of the internal combustion engine and an exhaust gas turbine coupled to the compressor in an exhaust gas duct of the internal combustion engine, wherein there is provided at least one bypass valve for bypass of the compressor and/or for bypass of the exhaust gas turbine.
2. Description of Related Art
In the connection of power generating installations with a generator which is to be connected to a power supply grid, the respectively prevailing grid and system rules of the corresponding power supply grid operator are to be taken into account. Those grid and system rules which are also referred to as the “Grid Code” or “Transmission Code” lay down, inter alia, technical minimum requirements and operating procedures of power generating installations in the event of a grid fault in the power supply grid. In that respect, grid faults in the form of dynamic grid voltage drops, which are also known by the term “low voltage ride through” (LVRT) events, are of relevance. Upon the occurrence of such a dynamic grid voltage drop, it is desirable for the electric phase angle, which is also referred to as the load angle or rotor displacement angle, to remain within predetermined limits as otherwise this can involve a pole slippage at the generator and, as a further consequence, uncontrolled accelerations of the internal combustion engine coupled to the generator. In addition, in the event of a grid restoration after the grid fault disappears, the mechanical loadings on the generator, the internal combustion engine and the coupling between the internal combustion engine and the generator increase with an increasing phase angle change.
A conventional measure for keeping the phase angle change within predefined limits is to deactivate the ignition in an internal combustion engine coupled to the generator. In the case of an internal combustion engine with turbocharger, however, the operating point in the compressor characteristics is shifted in the direction of the surge limit due to the ignition being switched off. If the surge limit is exceeded, that results in a stall at the compressor vanes of the turbocharger and so-called compressor surge occurs, which, as a further consequence, can lead to an unstable operating condition with respect to the internal combustion engine.